Optically Active P₅‐Deltacyclenes: A Unique Cage‐Inversion Reaction and Some Transition‐Metal Complexes of the Rearranged Cage

Abstract

Cage-chiral P 5 -deltacyclene 1 is available as a pair of highly enriched P-C cage enantiomers 1′ and 1′′, which exist as pairs of epimers a and b. Deprotonation of cage atom P1 initiates a rearrangement reaction, in which P1 and the neighboring carbon atom C4, together with its substituent, change places to form optically active iso-P 5 -deltacyclene enantiomers 6′′ and 6′, again as pairs of epimers. The CD spectra of related pairs of optically active cages 1 and 6 consist of almost mirrorsymmetric curves, an indicator of mirror-symmetric cage structures. This surprising result was verified by an absolute structure determination of the W(CO) 5 complex 9a′′. With the exception of the two cage nuclei that had changed places in relation to starting material 1′, all other cage nuclei of rearrangement [a] 691 Scheme 2. Base-induced cage-rearrangement reactions of 1′ and 1′′ to form 6′′ and 6′, respectively. Expected and experimentally observed reaction pathways.

Optically active P5-deltacyclenes: selective oxidation, ligand properties, and a diastereoselective rearrangement reaction

“…In comparison to 5a,b, the spectra of the oxidation products 9-11 agree with unchanged P 5 -deltacyclene cage structures and the unit P1-H1 forming epimers. 21 Some general trends are observable. The strongest influence of the oxidation on the spectra concern P1 of the oxo species 9a and 9b, due to Scheme 4 Preparation of P5-thio-tetra-tert-butyl-P 5 -deltacyclene epimers 10a and 10b, P5-seleno-tetra-tert-butyl-P 5 -deltacyclene epimers 11a and 11b and tri-seleno-tetra-tert-butyl-P 5 -tetracycloundecane 12.…”

“…One of the most impressive properties of 5 is a base induced cage rearrangement reaction that includes the complete inversion of the cage and proceeds without loss of the optical activity for 5′ and 5″. 21 Oxidation of the cage should influence that reaction significantly. P-C cage rearrangement reactions are in most cases accomplished by photochemical activation, but nothing is known about the stereochemical aspects of these reactions.…”

“…(Scheme 8) P1 and C4 change places in both cases, but preparation of 19 from 5 includes a unique cage inversion process which transforms 5′ into 19″. 21 For 16, and the same c One of two independent pairs of enantiomers in the unity cell. In the case of 10a and 11a one of the t-Bu groups of the second pair of enantiomers is disordered.…”

Stereoselective P5-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds

“…A novel aspect of this field of chemistry are optically active derivatives of chiral P‐C cage compounds . As a specific property of the derivatives of 3 , a once established enantiomeric excess remains untouched by all reactions tested to date which do not disintegrate the molecules such as destannylation, protonation, deprotonation, complexation,, oxidation, and cage rearrangement including cage inversion . In spite of its five P‐lone pairs and a dynamic equilibrium between two epimers, P‐H P 5 ‐deltacyclene 5 (Scheme ) proved to be a highly selective ligand with metals of interest for catalytic applications.…”

“…To pave the way for further developments of the chemistry of optically active P 5 ‐deltacyclene derivatives, we hereby report about the substitution of the P‐H function of tetra‐ tert ‐butyl‐P 5 ‐deltacyclene ( 5 ) by organyl groups. The classical route of deprotonation and introduction of electrophiles is not applicable because of a rapid cage rearrangement of deprotonated [ 5 – H] – , . P‐alkylation of a P‐C cage compound has been reported for the first time for tetraphosphacubane ( 1 ), and an asymmetric P‐C cage has been used as well .…”